1. Field of the Invention
The present invention relates to a rotation angle detecting device, provided at an end of a camshaft of an internal combustion engine, which detects a rotation angle of the camshaft.
2. Description of the Prior Art
FIG. 4 is a cross sectional view showing a structure of a conventional rotation angle detecting device. In FIG. 4, the reference numeral 1 denotes a housing of a rotation angle detecting device. The housing is composed of an aluminum casting or the like, and mounted on an internal combustion engine 4 while being positioned by a mounting surface 2 and a spigot portion 3 in the axial direction and the radial direction respectively. Reference numeral 5 denotes a shaft of the rotation angle detecting device. The shaft 5 is supported on the housing 1 with bearings 6 and 7, and connected to a camshaft 9 of the internal combustion engine 4 through a coupling 8. Further, the shaft 5 is rotated in synchronism with the camshaft 9, and a vane 10 which acts as a rotor of the rotation angle detecting device is secured to an end of the shaft 5.
The vane 10 is made of a magnetic material and cup-shaped. As shown in FIG. 5, one or more wall portions 12 are provided on the cylindrical portion 11 of the vane 10. The reference numeral 20 denotes a sensor mounted on the housing 1. The sensor 20 is composed of a first yoke 21 of a magnetic material, a second yoke 22 of the same magnetic material, which is opposite to the first yoke 21, a magnet 23 secured on the first yoke 21, a magnetic flux detector 24 such as a Hall element or the like, which is opposite to the magnet 23, and a subhousing 25 which holds them. The subhousing 25 is molded with synthetic resin and at the same time, a connector portion 26 which projects outside the housing 1 is integrally molded. Further, a terminal 27 is formed at the interior of the connector portion 26. The subhousing 25 is also molded so that a plurality of conductors 28 form an interconnection to the Hall element. A slit 29 is provided between the first yoke 21 and the second yoke 22 which is opposite thereto, and between the magnet 23 and the magnetic flux detector 24 which is opposite thereto. In the slit 29 rotates the wall portion of the cylindrical portion 11 of the vane 10 while keeping space. A cover 30 shields the second yoke 22 and the magnetic flux detector 24: a top cover 31 of the housing 1, an oil seal, 32 an O-ring 33, and a packing 34 are provided in order to insulate the sensor from water or oil.
In thus formed conventional rotation angle detecting device, when the shaft 5 is driven by means of the camshaft 9, the vane 10 is rotated, and the wall portion 12 provided in the cylindrical portion 11 of the vane 10 passes through the slit of the sensor 20, in accordance with a rotation angle. When the wall portion 12 of the vane 10 is not inside the slit 29, the magnetic flux of the magnet 23 passes through a magnetic path formed by means of the first yoke 21 and the second yoke 22 which is opposite thereto, and also by means of the magnet 23 and the magnetic flux detector 24 which is opposite thereto. The output signal of the magnetic flux detector 24 reaches a low level L. When the wall portion 12 enters the slit 29, the magnetic flux of the magnet 23 passes through a magnetic path formed by the first yoke 21, the wall portion 12 of the vane 10 and the magnet 23. However, since the magnetic flux does not pass through the magnetic flux detector 24, the output signal is changed to a high level H.
Thus, the rotation angle detecting device is constructed in a manner that it transmits a signal H and a signal L repeatedly, in accordance with the rotation angle of the camshaft 9, and detects the rotation angle of the camshaft 9, i.e., the crank shaft of the internal combustion engine. Further, lubricating oil is required for the bearings 6 bearing the shaft 5, and the bearings 6 are supplied with the lubricating oil from the camshaft 9 side. In order to prevent the lubricating oil leak, an oil seal 32 and an O-ring 33 are provided. Further, in order to prevent the entry of water from the outside, the packing 34 is provided for the top cover 31, so that the space where the magnet 23, the magnetic flux detector 24 and vane 10 are located has a waterproof construction.
Thus formed conventional rotation angle detecting device has a number of components other than the sensor 20 and the vane 10 which are needed for essential functions, and requires many man-hours in additional manufacture and work of parts other than the essential functional parts. Further, many parts requires many man-hours in the assembly of the rotation angle detecting device.